<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        h1 {
            background-color: blue;
            height: 100px;
            /* width: 100%; */
            padding: 30px;
        }
        
        div {
            width: 100px;
            height: 100px;
            background-color: chartreuse;
            border: 5px black dotted;
        }
        
        div p {
            padding: 30px;
            background-color: coral;
            border: 5px black dotted;
            margin: 10px;
        }
    </style>
</head>

<body>
    <h1>hello</h1>
    <div>
        <p>ni</p>
    </div>
    <div>a</div>
    <div>b</div>
</body>

</html>